Unit 4 Assessment

Which of the following best explains why Earth is tectonically active?

• Earth’s solid surface layer rotates more rapidly than the layers beneath it.

• Areas of Earth’s solid surface layer are under great pressure from ocean water.

• Earth’s solid surface layer sits on a moving, semiliquid layer.

• Areas of Earth’s solid surface layer are thicker and so heavier than other areas

Oceanic crust is composed mainly of basalt. Continental crust is composed mainly of granite. Why does oceanic crust generally tend to subduct under continental crust when plates collide?

• The oceanic crust is thicker than the continental crust.

• The continental crust is thicker than oceanic crust.

• The oceanic crust is denser than the continental crust.

• The continental crust is denser than the oceanic crust.

Which scale is used to report the intensity of an earthquake?

• Saffir­ Simpson Scale

• Modified Mercalli Scale

• Richter Magnitude Scale

• Moment Magnitude Scale

Tectonic motion caused tension between plates in Earth’s crust. A sudden release of this energy occurred. Based on this information, which event happened?

• subsidence

• earthquake

• volcanic eruption

• meteoroid impact

Which ongoing process causes the buildup of energy that is released at a later time when an earthquake occurs?

• Heat from Earth’s core slowly melts the rocks found deep in Earth’s crust.

• Nuclear reactions in Earth’s lower crust release electromagnetic waves.

• Jagged edges along a fault generate friction between two moving tectonic plates.

• Tectonic plates near a fault continue to move even though the fault remains motionless.

Which statement describes an aspect of tectonic plate motion directly caused by density differences among tectonic plates?

• Ocean plates move outward from the mid­ocean ridge.

• When ocean and continental plates collide, the ocean plate is subducted.

• Continental plates are thicker and contain older material than ocean plates.

• The orientation of magnetic particles in ocean plates changes at regular intervals.

A volcano found in the center of a tectonic plate tends to be a result of which phenomenon?

• strong earthquake

• activity at a hot spot

• pressure in thick sediments that produces heat

• unusually excessive erosion that wears away bedrock

In 1911 Alfred Wegener read a scientific paper that listed identical fossils found on distant continents. How did this evidence contribute to the modern theory of how the continents resulted in their current shapes?

• by showing that the cooling of Earth helped produce continents

• by suggesting that forces have caused continents to separate over time

• by showing that biological evolution is similar on separate continents

• by suggesting that liquid rock in the mantle solidifies in the continental crust

Earthquakes can be severe along the San Andreas Fault in Southern California, but volcanoes are nonexistent. Which statement best explains this pattern? A. B. C. D.

• The crust is thin and weak at the location of this fault.

• The material along this fault is smooth and fine grained.

• The material in the mantle solidified due to cooling under this fault.

• The crustal plates slide along each other without subducting at this fault.

A fold observed in layers of sedimentary rock most likely resulted from the

• cooling of flowing magma.

• converging of crustal plates.

• deposition of river sediments.

• solution of carbonate minerals.